William Crosson, a 28-year-old executive recruiter and part-time D.J., wears V-Moda Crossfade Wireless headphones, a $270 set that looks like something a cyberhooligan might wear to a Berlin disco.

Alexander Gilkes, a member of Vanity Fair’s best-dressed list and co-founder of the auction site Paddle8, wears $400 headphones made by Master & Dynamic.

Martin Gaynor, a 27-year-old freelance app developer for the New York City Department of Parks and Recreation, wears Symphonized 2s, a pair of wood-covered, over-the-ear headphones that he bought on Amazon for $53. “The wooden earthy look just seemed to complement the subdued classical look I have on a day-to-day basis,” he said. “It just matched.”

Don’t forget the cultural bellwether Beyoncé. In her “Lemonade” video this year, she belts out “Sandcastles,” a ballad of a woman scorned, while wearing $550 Prymas.

Global headphone sales hit a peak of $8.4 billion in 2013, and two years later, that figure rose to $11.2 billion, according to the research firm Futuresource Consulting. The company predicts that sales will rise another $2 billion by 2018, meaning we have yet to reach Peak Headphone.

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Alexander Gilkes listening to his Master & Dynamic MH 40 headphones near Cooper Union.CreditJonno Rattman for The New York Times

The combination of the iPhone and headphones in many varieties (in-ear, over-the-ear, shaped-to-your-ear and so on) gives city dwellers the ability to largely avoid an experience that was once arguably the whole point of living in the crowd — interacting with others.

In a fraught public sphere, headphones provide a measure of privacy. Those who fall deeply into a Spotify playlist or the latest installment of an addictive podcast enter a cocoon-like zone all but impenetrable to tourists, beggars and those do-gooders with clipboards.

“Headphones are the front line of urban social defense,” said Julie Klausner, a comedian, actor and writer. “I’m introverted and socially anxious by nature. My worst nightmare is sitting next to someone on a plane or someone who wants to strike up a conversation on an elevator.”

But Ms. Klausner knows she opens herself to experiences she may otherwise miss when she leaves the headphones at home.

“The other morning, I forgot my headphones and was on the 2 train going to physical therapy when I spilled water over my own seat,” she said. “Then this smiling older woman came over to talk. If my headphones had been on, that probably wouldn’t have happened.”

Alone Together

On a recent Thursday in Midtown Manhattan, Grimaldi Perdomo, 37, an architect, was on his way to work, wearing a Burberry trench coat and listening to the Weeknd’s new album, “Starboy,” on his Parrot Ziks, popular $400 black and titanium headphones designed by Philippe Starck.

A look through Mr. Perdomo’s black Banana Republic bag revealed that he, like other urban warriors, has headphones for all occasions.

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Martin Gaynor wearing Symphonized 2.0 headphones on Amsterdam Avenue.CreditJonno Rattman for The New York Times

Tucked into a small cardboard box was a pair of white Jaybird wireless in-ear headphones for the gym. Should the Jaybirds fail, Mr. Perdomo had a backup: trusty white Apple earbuds, the minimalist sound-delivery system that was all the rage not so long ago but has increasingly been replaced by more garish accessories. At home, Mr. Perdomo said, is an old pair of Beats.

“I like my music,” he said.

All the same, he believes something has gotten lost as many people navigate public spaces under the spell of the private experiences encouraged by digital media.

“Technology has ruined us,” Mr. Perdomo said. “You go to a restaurant and look around, and maybe 80 percent of the people are looking at their phones.”

Please Go Away

The experience of intense private listening in public settings is nothing new. It goes back to teenagers communing with the Shangri-Las via the earpieces connected to transistor radios in the 1950s and ’60s. It recalls the Sony Walkman craze of the ’80s.

But the latest round of headphones popularity may be an expression of our disaffected times, coming during a season when people holding different views on matters political and cultural struggle to open their mouths without triggering an argument.

Some headphones are chrome and accentuate the bass. Others are gold and boost the treble. The companies producing them can go from obscure to white-hot overnight.

Enormous growth has taken place for headphones priced from $99 to $500. But companies like HiFiMan, Audeze and JH Audio have built substantial businesses selling headphones that retail for as much as $3,000.

There is even a Broadway show, “The Encounter,” by Simon McBurney, experienced through headphones. It opened to rave reviews in September, with its fancy listening devices given, free of charge, by the German headphones brand Sennheiser. The irony of “The Encounter” is that it relies on state-of-the-art technology to deliver a lament against it.

The Shift

The paradox of the headphone experience — which somehow brings together, as Mr. McBurney suggested, isolation and intimacy — did not seem to be on the mind of Val Kolton, 39. A sports-car-obsessed techno fanatic, he founded a headphones company in 2004, naming it V-Moda because “‘moda’ means fashion,” he said, and all his favorite brands were Italian.

Before starting his business, Mr. Kolton was living in San Diego and working at Aviatech, a digital marketing company. Then he had an awakening on a dance floor in Ibiza, Spain.

“We were doing antismoking commercials, and I heard we were going to do another for Mothers Against Drunk Driving,” Mr. Kolton said one evening this fall, as he sat on a black leather sofa in his West Hollywood offices. “And I was having a drink and a smoke, and I thought: ‘You know what? Why am I doing all these “anti” campaigns? What’s next? An antisex campaign? Dance music is going to break through. House music is here!’”

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Corman Sheridan from Northern Ireland listens to Phillips headphones while doing yoga on the Great Lawn of Central Park.CreditJonno Rattman for The New York Times

Two years later, Mr. Kolton’s parents gave him money to produce candy-colored $99 earbuds. At the time, Apple was scheduled to release the first iPhone, with a recessed headphone jack that was incompatible with most headphones on the market.

Mr. Kolton got the bright idea of manufacturing his line to Apple’s market-busting specifications. He flew to Cupertino, Calif., and made the pitch. He figured he would be one of many entrepreneurs with Apple in mind, but that was not the case.

The market got more crowded after Beats by Dr. Dre, founded by Andre Young, known as Dr. Dre, and the music producer and executive Jimmy Iovine, introduced its first $300 headphones in 2008.

“Before Beats, $300 for a headphone was considered an outrageous amount of money to spend,” said Jamey Warren, the chief executive of Headphone.com. “You could buy a Sennheiser HD 600 over-the-ear headphone for $300. It was considered the world’s best, and it was a stretch for most folks except audiophiles.”

Increased demand isn’t the only thing fueling the boom. Crowdfunding sites have given potential entrepreneurs new routes to capital, while manufacturing costs have fallen. The 2014 sale of Beats to Apple, for $3 billion, also ushered in a new wave of headphone hopefuls.

Steve Guttenberg, a contributing editor to the digital products review site CNET and a high-fidelity expert, explained how the business has changed.

“Thirty years ago, when someone said, ‘I want to make a headphone,’ he would probably try to make it here in the United States, or he might design it and then get on a plane and say to the people who make headphones in China: ‘Here’s the design. Can you execute it?’” he said. “Now, we’ve eliminated the first two steps. The requirement, quote unquote, is that the person who’s running the show knows what it should sound like and look like and feel like and is able to say, ‘Keep showing me your samples until I find it.’”

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Daniel Villano listens on JH 13s in-ear monitors on West 54th Street.CreditJonno Rattman for The New York Times

By the time Jonathan Levine, 54, a former investment banker at Lehman Brothers, started the headphones company Master & Dynamic in 2014, it was clear that design and marketing were key.

Mr. Levine settled on the brand name Master & Dynamic because it sounded similar to established audio brands such as Bang & Olufsen, Astell & Kern, and Bowers & Wilkins. “‘Levine’ didn’t exactly scream luxury,” he said.

To get out the message for his 1950s-inspired, produced-in-China headphones, with its cognac-colored headband, he hired Carolina Clouet, a Balenciaga-clad former consultant for Barneys and Neiman Marcus, as his director of sales.

In October 2014, Bergdorf Goodman, Opening Ceremony and Colette received the first shipments of Mr. Levine’s pièce de résistance, the $399 MH40. In December of that year, Mr. Levine’s team sent them as freebies to Art Basel Miami Beach attendees at the Edition hotel and the Standard Miami.

After David Beckham began wearing them around Los Angeles, GQ proclaimed them “The Most Stylish Headphones Money Can Buy.” By the end of 2015, Master & Dynamic’s staff increased to 36 employees, from eight, who now work in a loftlike space in the garment district, where the walls are adorned with artwork by Christian Marclay and Terry Winters. There is even a Chuck Close portrait of Philip Glass, who, Mr. Levine was pleased to say, wears Master & Dynamics.

While many celebrities serve as brand endorsers, unwitting or not, others are trying to become the brand. This year, Will.i.am, a longtime minority partner in Beats, started Buttons, a $200 set of wireless, in-ear headphones shaped like small saucers and sold through Apple. The fashion stalwart André Leon Talley is the creative director, styling the ads and the boxes, which star Naomi Campbell and Kendall Jenner.

“Nobody has made a fashion headphone that’s in-ear,” Will.i.am said by phone while on a break from taping the British edition of “The Voice.” “They’re all big headphones that sit over your head. The reason we went with earbuds is because we were designing it to be like jewelry.”

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A woman with earbuds at the Columbus Square fountain.CreditJonno Rattman for The New York Times

The countless options can be paralyzing to customers. The writer and radio host Kurt Andersen said he had trouble picking the right headphones as he perused CNET’s exhaustive review section recently.

“I like that the over-the-ears are not as dorky as they once were,” he said. “The ones from Beats seem fine. But then do I look like someone trying to be young, with groovy, hip-hop headphones?”

The Holdouts

A challenge for the industry is getting women interested in its high-end gear. Amy Uaarmorn, a 31-year-old staff member at the Chateau Marmont hotel in Los Angeles, received a free pair of Master & Dynamic MH40s last year. Yet she said she seldom wears them and cannot imagine spending any more than $50 or $100 on headphones.

Never mind that Ms. Uaarmorn’s former boyfriend, Brannan Mason, 24, happens to be the co-owner of Noble Audio, a three-year-old Santa Barbara company that has received glowing notices for its in-ear earphones with prices that begin at $300 and go to $2,700.

Some of the ultraexpensive headphones are made to fit your ear exactly. To get a pair, you see an audiologist, who takes impressions of yours ears using a Play-Doh-like substance and ships them off to a manufacturer like Noble Audio.

This variety, known as CIEMs (short for custom in-ear monitors), started with touring musicians, who use them to block ambient noise and monitor their own sound.

Julie Glick, an audiologist who has a practice on Park Avenue, operates almost like a pharmaceutical rep for Noble Audio and other brands that specialize in custom, in-ear headphones. Matt Stone, a creator of “South Park,” and Daniel Villano, a colorist at Frédéric Fekkai, are among her clients who pop in to test demo units. When a sale is made, she earns a commission.

The trend really took off when JH Audio, a big player in this area, began posting photos of its famous customers and their CIEMs on Facebook and Instagram.